A carbon nanotube has been expected to find use in various functional materials because of, for example, its excellent thermal and electrical characteristics. Accordingly, various investigations have been conducted on the productivity, applications, and the like of the carbon nanotube. For example, the following is given as an approach to putting the carbon nanotube into practical use as a functional material. A carbon nanotube aggregate formed of a plurality of carbon nanotube columnar structural bodies is prepared, and the characteristics of the aggregate are improved.
An application of the carbon nanotube aggregate is, for example, a pressure-sensitive adhesive (Patent Literature 1 and Patent Literature 2). Although various materials have been used in pressure-sensitive adhesives for industrial applications, most of the materials are each a viscoelastic body designed to be a soft bulk. The viscoelastic body wets, and conforms to, an adherend because of its low modulus, and then exerts its adhesive strength. On the other hand, it has been revealed that as its diameter is of a nanometer size, the carbon nanotube follows the surface unevenness of the adherend and then exerts its adhesive strength by virtue of a van der Waals force.
A carbon nanotube composite structural body including, on a base material, the carbon nanotube aggregate formed of the plurality of carbon nanotube columnar structural bodies is applicable to various applications such as a pressure-sensitive adhesive member.
The carbon nanotube composite structural body is generally produced by growing and forming the carbon nanotube on the base material by a chemical vapor deposition method (CVD method). The growth and formation of the carbon nanotube by the chemical vapor deposition method (CVD method) are generally performed under a high temperature of about 400 to 800° C. Accordingly, a highly heat-resistant material showing high durability even under high temperatures is used as the base material. However, the base material formed of such highly heat-resistant material involves a problem in that the base material has a low adhesion strength with the carbon nanotube. When the adhesion strength between the carbon nanotube and the base material is low as described above, the application of the carbon nanotube composite structural body to, for example, a pressure-sensitive adhesive member involves the following problem. The carbon nanotube aggregate formed of the plurality of carbon nanotube columnar structural bodies needs to be transferred onto another base material, and hence a production cost increases.
Heretofore, a silicon substrate has been representatively used as the base material in which the highly heat-resistant material is used. However, the silicon substrate involves a problem in that the silicon substrate is expensive. In addition, the following problem arises. The silicon substrate is hardly applied to an application where flexibility (for example, such flexibility that the substrate can be bent by 180°) is requested because the substrate is rigid. Further, the following problem arises. The silicon substrate is considerably inferior in thermal conductivity and electric conductivity to the carbon nanotube.
In view of the foregoing, attention should be paid to a base material except the silicon substrate as the base material in which the highly heat-resistant material is used. However, such base material involves a problem in that the base material has an extremely low adhesion strength with the carbon nanotube.